Ultrasonic instruments, including both hollow core and solid core instruments, are used for the safe and effective treatment of many medical conditions. Ultrasonic instruments, and particularly solid core ultrasonic instruments, are advantageous because they may be used to cut and/or coagulate organic tissue using energy in the form of mechanical vibrations transmitted to a surgical end-effector at ultrasonic frequencies. Ultrasonic vibrations, when transmitted to organic tissue at suitable energy levels and using a suitable end-effector, may be used to cut, dissect, or cauterize tissue. Ultrasonic instruments utilizing solid core technology are particularly advantageous because of the amount of ultrasonic energy that may be transmitted from the ultrasonic transducer through the waveguide to the surgical end-effector. Such instruments are particularly suited for use in minimally invasive procedures, such as endoscopic or laparoscopic procedures, wherein the end-effector is passed through a trocar to reach the surgical site.
Ultrasonic vibration is induced in the surgical end-effector by, for example, electrically exciting a transducer which may be constructed of one or more piezoelectric or magnetostrictive elements in the instrument hand-piece. Vibrations generated by the transducer section are transmitted to the surgical end-effector via an ultrasonic waveguide extending from the transducer section to the surgical end-effector.
U.S. Pat. No. 5,322,055 describes an ultrasonic surgical apparatus that includes a surgical instrument having a transducer for converting an electrical signal into longitudinal vibratory motion. The longitudinal vibratory motion is transmitted to an ultrasonic blade that is connected to the hand-piece. An accessory is releasably connected to the hand-piece to enable clamping of tissue against the vibrating blade to afford improved coagulating and cutting of tissue. In U.S. Pat. No. 5,322,055 scissors-like grips actuate a pivoted clamp jaw along one side of the ultrasonically vibrating blade to compress and bias tissue against the blade in a direction which is substantially normal to the direction of longitudinal vibratory motion.
Hemostatic devices have been described in various instruments for cutting, cauterization, coagulation or tissue welding. Most of the devices used are either monopolar or bipolar, for example, bipolar forceps, monopolar or bipolar scissors, and cutting and coagulating devices. See, for example, U.S. Pat. No. 5,707,369 that describes a temperature feedback system for closed loop control of the tissue temperature induced by the surgical instrument wherein a function of the temperature is used to determine when coagulation of tissue has occurred to a desired degree.
Although open loop energy instruments have been used successfully to control bleeding during surgical procedures, when such instruments are used, the primary control is the experience of the surgeon who responds to what is observed to be happening to the tissue as it is treated with energy. Often, particularly for endoscopic procedures, surgeons cannot readily see what is happening to the tissue. In addition, tissue properties may change quickly during energy delivery. A surgeon's reaction time may be insufficient for optimal efficacy. Consequently, the tissue treatment may not be as precisely controlled as may be desirable. Some problems that may occur include tissue charring, sticking of the tissue to the electrodes of the surgical instrument, and over or under treatment of the tissue.
Temperature-measuring devices have been described for use with tissue treating instruments to measure temperature and determine when the absolute temperature has exceeded a desirable temperature. These devices are typically used to signal to a user to turn off energy or to cause a control device to turn off or attenuate energy when the temperature has reached a level at which tissue sticking to the instrument may occur. Other instruments have used temperature feedback to maintain a set temperature to follow a predetermined temperature profile.
Notwithstanding these control arrangements, there is a continuing need for improvement in the control of heat energy delivery to the tissue and/or determination of when tissue treatment has reached an optimal level. In particular there is a need to provide a device and method for ultrasonic instruments that must perform both cutting and coagulating functions, and to provide closed loop feedback for separate cutting and coagulating aspects. This invention fulfills these needs.